1. Technical Field
Embodiments of this disclosure relate to a liquid ejection head and an image forming apparatus including the liquid ejection head.
2. Description of the Related Art
Image forming apparatuses are used as printers, facsimile machines, copiers, plotters, or multi-functional devices having two or more of the foregoing capabilities. As one type of image funning apparatuses employing a liquid-ejection recording method, for example, inkjet recording apparatuses are known that use a recording head (liquid ejection head or liquid-droplet ejection head) for ejecting droplets of liquid (e.g., ink).
In a liquid ejection head, when an individual channel is pressurized to eject a droplet, pressure fluctuation occurring in the individual channel is changed into a pressure wave and the pressure wave is also propagated to a common liquid chamber (a common channel) for supplying liquid to plural individual channels. When the pressure wave propagated to the common liquid chamber is inversely propagated to the individual channel, the pressure of the individual channel is caused to fluctuate so that a meniscus of a nozzle cannot be controlled. Consequently, a droplet cannot be ejected at a desired droplet speed and a droplet amount (droplet volume) or no droplet is ejected. When the pressure wave propagated to the common liquid chamber is propagated to an adjacent individual channel so that mutual interference influencing the liquid occurs, unintentional leakage or ejection of a droplet from the nozzle or instability of an ejection state is induced.
Hence, for example, in an art like described in JP-2011-056924-A, a part of a wall surface of a common liquid chamber is formed as a deformable damper area to attenuate a pressure wave propagated to the common liquid chamber, and a channel plate has such a size that an end surface in a direction perpendicular to a nozzle array direction does not reach the damper area in order to reduce the size thereof.
An attenuation effect (damper performance) produced by the damper area is proportional to a deformation amount (volume change rate) of the damper area, and the deformation amount is proportional to a first power of a long side, a fifth power of a short side and a minus third power of a thickness if the damper area takes a rectangular shape seen on a plane. Accordingly, increasing the short side of the damper area is effective for enhancing the damper performance.
When the short side of the damper area provided on a liquid ejection head has a length in a direction perpendicular to a nozzle array direction and the long side of the damper area has a length in the nozzle array direction, an increase in the short side of the damper area causes an increase in the length (referred to as “head width”) in the direction perpendicular to the nozzle array direction of the head, resulting in an increase in the size of the head.
On the other hand, when maintenance and recovery operations are carried out to maintain the performance of the liquid ejection head, a nozzle face of the head is capped with a cap member. In order to reliably carry out the capping of the nozzle face with the cap member, the length (head width) of the short side of the head is increased to secure an area capped by the cap member.